A known walk-in apparatus is disclosed, for example, in the U.S. Pat. No. 6,341,819 as a seat slide device for a vehicle. The walk-in apparatus has been known comprising a slide rail mechanism which slidably supports the vehicle seat in longitudinal direction relative to the vehicle floor, a lock plate which locks the slide rail mechanism and restrict the slide movement of the slide rail mechanism, a release lever which engages with the lock plate and releases the lock plate from the slide rail mechanism, and a supporting lever which engages with the release lever to keep the engaging condition between the lock plate and the release lever under a predetermined condition. A reclining plate, which rotates in conjunction with a pivotal movement of the seat back when the seat back is tilted more than or equal to a predetermined angle in forward direction of the vehicle by an actuation of a reclining arm mechanism which rotatably and adjustably supports the seat back of the vehicle seat, is connected to the release lever with the a rod.
However, the reclining plate and the rod are connected with a certain allowance in longitudinal direction of the rod, which allows the reclining plate to independently rotate in one direction. Position of the release lever relative to the slide rail mechanism is controlled through the rod by the reclining plate which is contacting with and supported by a certain portion of the reclining arm mechanism. On this account, the position of the release lever relative to the lock plate is easily affected by difference of the position and the size of the reclining plate, the rod and so on. As a result, the walk-in apparatus loses its stability. Thus, the walk-in apparatus needs to be comprised in consideration of reducing the difference of the position of the release lever relative to the lock plate and the supporting lever.